This invention relates to audio units and specifically to audio units capable of switching between radio broadcast and recording playback modes.
With increasing traffic congestion, radio stations are broadcasting traffic information on dedicated frequency bands. For example, such broadcasts are transmitted in some areas on AM band at 1620 Khz. These broadcast transmissions are receivable by automobile radios, permitting drivers to learn about, and respond, to traffic problems while driving.
To avoid missing important traffic information, a driver is ordinarily forced to surrender the use of his car's cassette player or other audio source so that the driver can monitor a traffic information broadcast continuously. Alternatively, he can switch intermittently between a traffic information station and other audio sources.
To permit the driver to stay apprised of important traffic information while listening intermittently to other broadcasts or recordings, a car audio unit can be provided with a switch, known as an ISR switch. The driver presses the ISR switch once while listening to one audio source such as a recording or other radio station. This causes the audio unit to output a traffic information broadcast at a preset frequency The driver presses the ISR switch again to switch back to the original audio source.
Another system employing an ISR switch, is disclosed in Japanese laid-open patent publication SN62-107490. This system allows the driver to switch between playback of a recording and a traffic information broadcast. When the ISR switch is activated during playback of a recording, the system pauses the playback. When the driver presses the ISR switch again, the playback of the recording begins where it left off so that the driver misses none of the recording.
Outside Japan, extensive use has been made of systems that announce traffic information broadcasts using identification signals that are superimposed on FM broadcasts. One type of signal, called a DK signal, is transmitted by Traffic Information Identification (ARI) broadcasts. A second type, called a TA signal, is transmitted by Radio Data System broadcasts (RDS).
Audio units such as disclosed in Japanese laid-open Utility Model Publication SN4-26983, pause the currently-selected audio device when the DK signal is received. Audio from the traffic information broadcast is then output. For example, when a DK signal is received while a tape player is playing a tape, the tape playback mode is paused, halting the tape. After the traffic information broadcast is completed, the playback recommences where it left off.
When prior art devices such as disclosed in Japanese Laid-open Utility Model Publication SN62-107490 and Japanese Laid-open Utility Model Publication SN4-26983 receive a traffic information transmission, the tape is paused during normal playback mode. The playback mechanism is also paused when it is in non-playback mode such as fast-forward (FF-APC) and rewind (REW-APC) while the tape head is up (APC-mode). When the traffic information broadcast ceases, the recording must continue to perform the special playback mode from the point where the traffic information broadcast began.